Peeping in on the Process of Turning Caterpillar to Butterfly

Previously, researchers hoping to learn about metamorphosis had to dissect the chrysalis, which killed the developing insect inside

In elementary school, we learn that caterpillars turn into butterflies and moths through a process called metamorphosis. But what really goes on within the hardened chrysalis has continued to puzzle scientists. Now, computer tomography scans have allowed researchers to peep in on the caterpillar-to-butterfly action taking place inside the chrysalis, The Scientist reports.

Previously, researchers hoping to learn about metamorphosis had to dissect the chrysalis, which killed the developing insect inside. The key breakthrough about this new technique, they say, is that it allows them to study living tissue as it grows and changes.

Using series of dead individuals provides snapshots of presumably sequential development, but it can be unclear whether one insect’s third day in a chrysalis is really the same developmentally as another’s. CT scans can provide a more complete picture of how development proceeds.

In this new study, the team scanned nine painted lady chrysalises. Four of the insects died during the experiment while the other five hatched. In their results, the researchers focused on data derived from one of the insects in particular that provided the most detailed scans.

Here’s a video the researchers put together of their caterpillar’s gradual development into butterfly:

Rather than rewriting the story of butterfly development, the researchers told The Scientist, this experiment fills in missing details. For example, The Scientist describes:

The trachea did become visible surprisingly fast, within 12 hours after pupation, indicating that the structures either are more fully formed in caterpillars than previously thought or form very rapidly in pupae. While the trachea and the intestines showed up remarkably clearly, the “soft, gooey bits,” such as muscles and the central nervous system, were unfortunately invisible, Garwood said.

Lepidopterists, the scientists who study butterflies and moths, are not the only insect researchers who can benefit from CT scans. Many other arthropods—including beetles, flies, bees, wasps, ants and fleas—also go through metamorphosis.